A Survey of Load Pull Simulation Capabilities

A Survey of Load Pull Simulation Capabilities
A Survey of Load Pull
Simulation Capabilities
– How do they Help You
Design Power
Amplifiers?
1
Agilent EEsof EDA
IMS 2010 MicroApps
Andy Howard
Agilent Technologies
May 19, 2010
Outline
• Power amplifier design questions
• Basic load pull concepts
• Fast, simple load pull
• Adding power sweeps to see compression
• Constant power-delivered load pull
• Constant power-delivered source pull
• Using two input tones to see intermodulation distortion
• Load pull with a WCDMA source
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May 19, 2010
Power amplifier design questions:
What’s the best load?
How does the bias point affect performance?
Do I need to add stabilization networks?
What about device size or # of cells?
Can I get a particular output power from a device?
How far into compression when delivering that power?
Many different loads satisfy the output power requirement.
How do I choose the best one?
What about the load impedance at harmonic frequencies?
How do I choose the best source impedance?
How does the optimal load impedance vary with frequency?
With other swept parameters?
What is an efficient approach for running load pull simulations?
What signal source should I use when running load pull?
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Load pull concept
Two main techniques
Available
source
power held
constant
Available
source
power
optimized
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Power
delivered
held constant
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Load pull concept
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Some preliminaries: biasing and stability
Choose bias point based on
class of operation or vendor/
foundry recommendation
Add feedback for stability, as needed
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Start with fast, simple load pull
Available
source
power held
constant
Source Power
= 5 dBm
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Source Power
= 12 dBm
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Focusing on a smaller region of the Smith Chart
Source Power
= 12 dBm
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Add power sweeps to see compression
At each load reflection coefficient,
also sweep available source power.
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Compression curves at maximum output power
and maximum PAE loads
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Constant power-delivered load pull
You specify the power to be delivered to the load.
For each reflection coefficient the available source
power is optimized.
Available
source
power
optimized
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Power
delivered
held constant
May 19, 2010
Contours are all with
same power delivered
Power delivered=27 dBm
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Do you want maximum PAE or minimum gain
compression?
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Results with delivered
power goal set to 28 dBm
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Do you want maximum PAE or minimum gain
compression? (Pdel_dBm = 28 dBm)
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Run source pull to improve gain
Chose load for maximum PAE from previous simulations
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Choose source Z for maximum gain or minimum
gain compression
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What else could you simulate?
• Performance versus frequency
• Performance with two input tones
• Performance with modulated input signals
• Performance versus some other swept parameter
• Performance versus harmonic load impedance
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Two-tone swept power load pull
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Two-tone swept power load pull
Available source power swept from -10 to +12 dBm
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Constant power delivered load pull with two tones
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Do you want to maximize PAE or minimize
intermodulation distortion?
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Load pull with WCDMA signal
Read modulated data from file.
Scale signal amplitude by
Filter bank at amplifier
optimizing “SFexp” variable.
output for computing ACLRs.
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ACLR and PAE contours
Power delivered set to 27 dBm
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Do you want to maximize PAE or minimize ACLR?
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Review
• Power amplifier design questions
• Basic load pull concepts
• Fast, simple load pull
• Adding power sweeps to see compression
• Constant power-delivered load pull
• Constant power-delivered source pull
• Using two input tones to see intermodulation distortion
• Load pull with a WCDMA source
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May 19, 2010
For more information:
On the latest release of ADS:
http://www.agilent.com/find/eesof-ads
Supported ADS customers may download an updated
Load Pull DesignGuide with all these simulation setups from
our Knowledge Center:
http://edocs.soco.agilent.com/display/eesofkc/
Loadpull+DesignGuide+for+ADS+2009+Update+1+with+new+content
Please view our load pull videos:
http://www.youtube.com/watch?v=FTK1pEu1Z64
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May 19, 2010
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